In typical wireless communications systems, a frequency difference between the transmitter and receiver local oscillators can prevent the transmission of data. Additionally, because many systems utilize the same Local Oscillator (LO) for both receiver and transmitter functions, a large frequency offset can cause significant out-of-band interference.
In order to overcome this problem, prior systems have utilized differential detection of phase or applied the Discrete Fourier Transform to estimate the frequency error and apply an update to the Local Oscillator. However, these prior systems either ignored the effects of multipath interference or combined the automatic frequency control (AFC) with a RAKE receiver. Therefore, these prior techniques were not applicable for systems that use Multi-user Detection without a RAKE receiver.